Tensioning devices comprising a chain tensioner as well as a tensioning and guide rail are used quite generally wherever chain drives are used. A preferred field of application is, however, the use in internal combustion engines, in which a timing chain drive drives the camshaft by means of a timing chain. In this field of application, high demands have to be satisfied with respect to the strength of the rails as well as the sliding and guiding characteristics in the area of contact with the endlessly circulating drive chain, since the drive chain must be kept under a defined tension during operation. In addition, manufacturing tolerances and an elongation of the drive chain occurring in the case of prolonged use are compensated for by the tensioning device. Conventional tensioning or guide rails consist either completely of a suitable plastic material provided with a sliding-contact surface for contact with the drive chain or of a carrier body provided with a sliding lining. The carrier body, which may be configured as a metal carrier or as a fiber-reinforced plastic profile, may be provided with a separate low-friction sliding body so as to form the sliding lining in the area of the surface contacting the chain.
DE 296 02 917 U1 discloses a tensioning rail for a timing chain drive, comprising a carrier body made of fiber-reinforced plastics and a sliding body made of low-friction plastics. The carrier body and the sliding body are produced separately of one another as prefabricated units. During final assembly, the sliding body is mechanically connected to the carrier body by means of form-fit elements. In the case of the tensioning or guide rail according to DE 43 103 06 A1, however, the sliding body is injection molded onto a carrier body of fiber-reinforced plastics by means of an injection molding process. DE 197 19 732 C1 discloses a guide rail for a chain drive, said guide rail comprising two spaced-apart sliding sections arranged on a common carrier. In addition, reference DE 10 2007 026 939 A1 discloses an integrally formed sliding element for a chain drive, in the case of which the surface facing a chain has at least one recessed section, which is not in contact with the chain.
Although many of the tensioning or guide rail structural designs known in the prior art proved to be very useful in practice, it is, due to the general pressure for innovations in the field of automotive industry, constantly endeavored to improve existing structural designs and to adapt them to the increasing demands. In addition, there are always cases of use, which necessitate an adaptation of the structural design or a change in the basic concept, and in this connection it will always be necessary to take into account the fundamental demands on tensioning or guide rails, the lowest possible frictional resistance to the drive chain, a low weight and a compact structural design. In addition, tensioning or guide rails are mass-produced articles which, with respect to the high numbers of pieces involved, constantly necessitate that the materials and structural designs used are replaced by less expensive or synergetic concepts.